1. Field of the Invention
The present invention relates to an anti-fouling agent, especially, an anti-fouling agent comprising an aqueous solution containing a polyvinyl alcohol.
Moreover, the present invention relates also to a method for producing the anti-fouling agent and to a method for producing a polymer using the anti-fouling agent.
2. Description of the Related Art
Heretofore, when vinyl chloride is polymerized alone or copolymerized with a monomer copolymerizable therewith in an aqueous medium by suspension polymerization, polymer scale deposits on the inner wall of a polymerization reactor, the surface of a stirring blade, the surface of a baffle, the inner wall of a pipe mounted in the polymerization reactor, the inner wall of a condenser and so on. The deposition of scale has resulted, for example, in decrease in cooling capacity of the polymerization reactor and deterioration of the quality of products caused by exfoliation and contamination of the depositions. Thus, the inner wall of a polymerization reactor must be cleaned every time polymerization has finished and this has caused the decrease in the operating rate of polymerization reactors and the increase in production cost. To solve these problems, the method of applying various kinds of anti-fouling agents onto the inner walls of polymerization reactors in advance has been proposed. JP-A 59-184208 discloses a method using a silanol-modified polyvinyl alcohol as an anti-fouling agent, but its effect of preventing the adhesion of scale is still insufficient.